Manipulator and path generation method thereof

ABSTRACT

A manipulator and a method of generating the shortest path along which the manipulator moves to grip an object without collision with the object models a target object and a gripper into a spherical shape, measures a current position of the gripper and a position of the target object and a target position of the gripper, calculates an arc-shaped path in a two-dimensional plane along which the gripper needs to move by calculating an included angle of a triangle consisting of the position of the object and the current position and target position of the gripper, transforms the arc-shaped path in the two-dimensional plane into an arc-shaped path in a three-dimensional space using a transform matrix consisting of the position of the object and the current position and target position of the gripper, thereby automatically generating the shortest path of the manipulator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.2011-0067069, filed on Jul. 6, 2011 in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

Embodiments relate to a method of generating the shortest path alongwhich a robot manipulator may move to grip an object without collisionwith the object.

2. Description of the Related Art

In general, machines which execute motions similar to those of humansusing an electric or magnetic action are referred to as robots.Industrial robots, such as manipulators and transfer robots forautomation and unmanned operation of production fields, which executedangerous operations, repeated operations, and operations requiringstrong force in place of humans were the first to be introduced.Recently, vigorous development of humanoid robots which have a jointsystem similar to that of humans and coexist with humans in humanworking and living spaces to supply various services to humans isunderway.

Such a humanoid robot executes an operation using a manipulator producedto move similar to the motion of a human arm or hand through anelectrical and mechanical mechanism. Most manipulators which are usednow are formed by connecting a plurality of links. A connection portionbetween the respective links is referred to as a joint, and motioncharacteristics of a manipulator are determined by geometrical relationsbetween the links and the joints. Mathematical expression of theserelations is referred to as kinematics, and most manipulators havingkinematic characteristics move a robot front end (hereinafter, referredto as a gripper) to a position at which an operation is executed.

In order to allow a manipulator to execute a given operation (forexample, an operation of gripping an object), generation of a movementpath of the manipulator from a current position (start point) prior toexecuting the operation to a position at which the operation isexecuted, i.e., a target position (target point) to grip the object, isrequired. At this time, the trajectory of the shortest path along whichthe manipulator may move from the current position to the targetposition without collision with the object needs to be generated.

SUMMARY

Therefore, it is an aspect to provide a method of generating theshortest path along which a robot manipulator may move to a targetposition without collision with an object during a process of grippingthe object in real time.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be obvious from the description, or may belearned by practice of the invention.

In accordance with one aspect, a movement path generation method of amanipulator to grip an object may include recognizing a current positionof a gripper provided at the front end of the manipulator, a position ofthe object and a target position of the gripper, calculating a rotaryangle in a plane from the current position of the gripper, the positionof the object and the target position of the gripper, calculating anarc-shaped path in a two-dimensional plane along which the gripper needsto move using the calculated rotary angle, calculating a transformmatrix consisting of the current position of the gripper, the positionof the object and the target position of the gripper, and transformingthe arc-shaped path in the two-dimensional plane into an arc-shaped pathin a three-dimensional space using the transform matrix.

The current position of the gripper may be a position of a start pointof the gripper prior to executing an operation of gripping the object.

The position of the object may be a central position of the object to begripped.

The target position of the gripper may be a position of a target pointof the gripper to grip the object.

The calculation of the rotary angle in the plane may include calculatingan included angle of a triangle formed by connecting the currentposition of the gripper, the position of the object and the targetposition of the gripper.

The calculation of the arc-shaped path in the two-dimensional space mayinclude calculating the sum of a radius of the object and a radius ofthe gripper, calculating an included angle by which the gripper movesfor a designated time, and calculating x and y coordinates in thetwo-dimensional plane to generate an arc-shaped trajectory bymultiplying the sum of the radius of the object and the radius of thegripper by the included angle by which the gripper moves for thedesignated time.

The calculation of the transform matrix may include transforming atriangular plane generating the arc-shaped trajectory from the currentposition of the gripper, the position of the object and the targetposition of the gripper into a three-dimensional matrix.

The transformation of the arc-shaped path in the two-dimensional planeinto the arc-shaped path in the three-dimensional space may includegenerating the arc-shaped path in the three-dimensional space alongwhich the gripper needs to move by multiplying the three-dimensionalmatrix by the x and y coordinates in the two-dimensional plane.

In accordance with another aspect of the present invention, amanipulator may include a gripper to grip an object, a plurality oflinks to move the gripper to a target position to grip the object, arecognition unit to recognize a current position of the gripper, aposition of the object and a target position of the gripper, and a pathgeneration unit to calculate an arc-shaped path in a two-dimensionalplane along which the gripper needs to move using the current positionof the gripper, the position of the object and the target position ofthe gripper, and to generate an arc-shaped path in a three-dimensionalspace along which the gripper needs to move using the calculatedarc-shaped path in the two-dimensional plane.

The path generation unit may include a two-dimensional path calculationunit to calculate the arc-shaped path in the two-dimensional plane usingthe current position of the gripper, the position of the object and thetarget position of the gripper, and a three-dimensional path transformunit to transform the arc-shaped path in the two-dimensional plane intothe arc-shaped path in the three-dimensional space by calculating atransform matrix consisting of the current position of the gripper, theposition of the object and the target position of the gripper.

The two-dimensional path calculation unit may calculate a rotary anglein a plane from the current position of the gripper, the position of theobject and the target position of the gripper, and calculate thearc-shaped path in the two-dimensional plane along which the gripperneeds to move using the calculated rotary angle.

The two-dimensional path calculation unit may calculate the sum of aradius of the object and a radius of the gripper, calculate an includedangle by which the gripper moves for a designated time, and calculate xand y coordinates in the two-dimensional plane to generate an arc-shapedtrajectory by multiplying the sum of the radius of the object and theradius of the gripper by the included angle by which the gripper movesfor the designated time.

The three-dimensional path transform unit may transform a triangularplane generating the arc-shaped trajectory from the current position ofthe gripper, the position of the object and the target position of thegripper into a three-dimensional matrix, and generate the arc-shapedpath in the three-dimensional space along which the gripper needs tomove by multiplying the three-dimensional matrix by the x and ycoordinates in the two-dimensional plane.

The manipulator may further include joints to drive the plurality oflinks to move the gripper along the path generated by the pathgeneration unit.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings of which:

FIG. 1 is a view illustrating the external appearance of a robot inaccordance with one embodiment;

FIG. 2 is a view illustrating main joint structures of the robot shownin FIG. 1;

FIGS. 3( a) and 3(b) are views schematically illustrating the shape of akinematically redundant manipulator of the robot in accordance with oneembodiment;

FIG. 4 is a block diagram illustrating a control system of a movementpath of a gripper of the manipulator of the robot in accordance with oneembodiment;

FIG. 5 is a view illustrating modeling of gripping of an object throughthe gripper in accordance with one embodiment;

FIG. 6 is a view illustrating an arc-shaped path in a two-dimensionalplane along which the gripper in accordance with one embodiment moves togrip an object;

FIG. 7 is a view illustrating an arc-shaped path in a three-dimensionalspace along which the gripper in accordance with one embodiment moves togrip an object;

FIG. 8 is a view illustrating an actual path along which the gripper inaccordance with one embodiment moves to grip an object; and

FIG. 9 is a flow chart illustrating a movement path generation method ofthe gripper of the manipulator of the robot in accordance with oneembodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments, examples ofwhich are illustrated in the accompanying drawings, wherein likereference numerals refer to like elements throughout.

FIG. 1 is a view illustrating the external appearance of a robot inaccordance with one embodiment.

As shown in FIG. 1, a robot 100 in accordance with one embodiment may bea bipedal walking robot which may move erect with two legs 110R and 110Lin the same manner as a human, and may include a torso 120, two arms130R and 130L and a head 140 provided at the upper portion of the torso120, feet 111R and 111L provided at the front ends of the two legs 110Rand 110L and hands 131R and 131L provided at the front ends of the twoarms 130R and 130L.

Here, R and L respectively indicate the right and left sides of therobot 100.

FIG. 2 is a view illustrating main joint structures of the robot shownin FIG. 1.

As shown in FIG. 2, the two arms 130R and 130L respectively may includeshoulder joints 132R and 132L, elbow joints 133R and 133L, and wristjoints 134R and 134L so that portions of the robot 100 corresponding toshoulders, elbows and wrists of a human may be rotatable, and theshoulder joints 132R and 132L may be located at both ends of the upperportion of the torso 120.

The shoulder joints 132R and 132L of the respective arms 130R and 130Lmay be movable in the x axis direction (in the roll axis direction), inthe y axis direction (in the pitch axis direction) and the z axisdirection (in the yaw axis direction), the elbow joints 133R and 133Lmay be movable in the y axis direction (in the pitch axis direction),and the wrist joints 134R and 134L may be movable in the x axisdirection (in the roll axis direction), in the y axis direction (in thepitch axis direction) and the z axis direction (in the yaw axisdirection).

The two arms 130R and 130L may further include upper links 135R and 135Lconnecting the shoulder joints 132R and 132L and the elbow joints 133Rand 133L to each other, and lower links 136R and 136L connecting theelbow joints 133R and 133L and the wrist joints 134R and 134L to eachother, thereby possibly moving with designated degrees of freedomaccording to movable angles of the respective joints 132R, 132L, 133R,133L, 134R and 134L.

A waist joint 121 allowing a portion of the robot 100 corresponding to awaist of a human to be rotatable may be provided on the torso 120connected to the two legs 110R and 110L, and a neck joint 141 allowing aportion of the robot 100 corresponding to a neck of a human to berotatable may be provided on the head 140 connected to the torso 120.

In one embodiment, each of the two arms 130R and 130L may correspond toa manipulator 130 executing an operation through which a motion may beachieved, and the hand 131R or 131L provided at the front end of themanipulator 130 may correspond to a gripper 131 to grip a target object.This will be described in brief with reference to FIGS. 3( a) and 3(b).

FIGS. 3( a) and 3(b) are views schematically illustrating the shape ofthe kinematically redundant manipulator of the robot in accordance withone embodiment.

As shown in FIGS. 3( a) and 3(b), the manipulator 130 may be configuredto move in a similar manner to a human arm or hand by an electrical andmechanical mechanism, and may be formed by connecting a plurality oflinks (in more detail, upper and lower links) 135 and 136 through aplurality of joints (in more detail, shoulder joints, elbow joints andwrist joints) 132, 133 and 134. Motion characteristics of themanipulator 130 may be determined by geometrical relations between thelinks 135 and 136 and the joints 132, 133 and 134. Mathematicalexpression of these relations is referred to as kinematics, and mostmanipulators having kinematic characteristics may move a gripper to aposition to perform an operation. The manipulator 130 in accordance withone embodiment may move the gripper 131 to a target position to grip anobject using the links 135 and 136, the positions and directions ofwhich are adjustable.

As shown in FIGS. 3( a) and 3(b), the shape of the manipulator 130moving to the target position to grip the same object may be varied.

FIG. 4 is a block diagram illustrating a control system of a movementpath of the gripper of the manipulator of the robot in accordance withone embodiment, possibly including a user interface unit 200, a pathgeneration unit 210, a recognition unit 220, a robot control unit 230,and a drive unit 240.

The user interface unit 200 may enable a user to input an operationcommand performed by the manipulator 130, particularly, the gripper 131(for example, a command to grip an object placed on a table) throughoperation of a switch or voice.

The path generation unit 210 may generate an operation path to controlmovement of the gripper 131 to grip a target object A without collisionwith the target object A according to the operation command inputthrough the user interface unit 200, and may transmit the operation pathto the robot control unit 230.

Further, the path generation unit 210 may include a two-dimensional pathcalculation unit 211 to calculate an arc-shaped path in atwo-dimensional plane along which the gripper 131 moves using a positionof the object A, a current position of the gripper 131 and a targetposition of the gripper 131, and a three-dimensional path transform unit212 to transform the arc-shaped path in the two-dimensional plane intoan arc-shaped path in a three-dimensional space along which the grippers131 moves by calculating a transform matrix consisting of the positionof the target object A, the current position of the gripper 131 and thetarget position of the gripper 131.

The recognition unit 220 may recognize information given for the gripperto execute the operation command, for example, the shape of the gripper131 at the current position (start point) prior to executing theoperation command, the shape of the gripper 131 at the target position(target point) to execute the operation command and the position of thetarget object A to be gripped, and may transmit the recognizedinformation to the path generation unit 201. Such recognized informationmay be used to generate the movement path of the gripper 131 by the pathgeneration unit 210.

A method of recognizing the position of the target object A and thecurrent position and the target position of the gripper 131 through therecognition unit 220 will be described later with reference to FIG. 5.

The robot control unit 230 may control the drive unit 240 according tothe movement path transmitted from the path generation unit 210 to drivethe manipulator 130, thereby controlling movement of the gripper 131provided at the front end of the manipulator 130.

Hereinafter, an operating process and functions and effects of theabove-described robot manipulator and a path generation method thereofwill be described.

FIG. 5 is a view illustrating modeling of gripping of an object throughthe gripper in accordance with one embodiment, FIG. 6 is a viewillustrating an arc-shaped path in a two-dimensional plane along whichthe gripper in accordance with one embodiment moves to grip an object,and FIG. 7 is a view illustrating an arc-shaped path in athree-dimensional space along which the gripper in accordance with oneembodiment moves to grip an object.

FIG. 5 illustrates modeling of the target object A and the gripper 131provided at the front end of the manipulator 130 into a spherical shape,on the assumption that the manipulator 130 grips the target object A.

In FIG. 5, the recognition unit 220 may recognize the position of thetarget object A, the current position of the gripper 131 and the targetposition of the gripper 131 as below.

First, the recognition unit 220 may model the target object A to begripped into a spherical shape, recognize a central position X_(obj) ofthe modeled spherical target object A as the position of the targetobject A, and transmit the position X_(obj) of the target object A tothe path generation unit 210.

Further, the recognition unit 220 may model the shape of the gripper 131before the manipulator 131 grips the target object A into a sphericalshape, recognize a central position of the modeled spherical gripper131, i.e., a position X_(c) of a start point before the gripper 131executes an operation to grip the target object A, as the currentposition of the gripper 131, and transmit the current position X_(c) ofthe gripper 131 to the path generation unit 210.

Moreover, the recognition unit 220 may model the shape of the gripper131 when the manipulator 131 grips the target object A into a sphericalshape, recognize a central position of the modeled spherical gripper131, i.e., a position X_(t) of a target point when the gripper 131executes the operation to grip the target object A, as the targetposition of the gripper 131, and transmit the target position X_(t) ofthe gripper 131 to the path generation unit 210.

Therefore, the two-dimensional path calculation unit 211 of the pathgeneration unit 210 may calculate an included angle of a triangle formedby connecting the position X_(obj) of the target object A, the currentposition X_(c) of the gripper 131 and the target position X_(t) of thegripper 131 transmitted from the recognition unit 220, i.e., a rotaryangle Ø in a plane, and may calculate an arc-shaped path in atwo-dimensional plane along which the gripper 131 needs to move usingthe calculated rotary angle Ø. Hereinafter, a method of calculating thearc-shaped path in the two-dimensional plane along which the gripper 131needs to move will be described.

On the assumption that a time taken for the gripper 131 to move from thecurrent position X_(c) of the gripper 131 before the gripper 131 gripsthe target object A to the target position X_(t) of the gripper 131 whenthe gripper 131 grips the target object A is referred to as ‘T’, an arcin a two-dimensional plane may be calculated by multiplying the sumR1+R2 of a radius R1 of the modeled spherical object A and a radius R2of the modeled spherical gripper 131 by the rotary angle Ø by which thegripper 131 moves for a designated time t (0<t<T, a path movement timefor which the gripper 131 may move without collision with the object A).Here, x and y coordinates in the two-dimensional plane to which thegripper 131 moves for the designated time t may be calculated byEquation 1 below.R(t)=(R1+R2)φ(t)x(t)=R(t)cos(φ(t))y(t)=R(t)sin(φ(t))  Equation 1

In Equation 1, R(t) represents an arc in the two-dimensional plane alongwhich the gripper 131 moves for the designated time t, and x(t) and y(t)represent x and y coordinates in the two-dimensional plane to which thegripper 131 moves for the designated time t.

As described above, when the two-dimensional path calculation unit 211of the path generation unit 210 calculates the arc-shaped path in thetwo-dimensional plane along which the gripper 131 needs to move bycalculating the rotary angle Ø in the plane consisting of the positionX_(obj) of the target object A, the current position X_(c) of thegripper 131 and the target position X_(t) of the gripper 131, thethree-dimensional path transform unit 212 of the path generation unit210 may generate a path in a three-dimensional space along which thegripper 131 needs to actually move using the calculated arc-shaped pathin the two-dimensional plane. Hereinafter, a method of calculating thepath in the three-dimensional space along which the gripper 131 needs toactually move will be described.

First, the three-dimensional path transform unit 212 of the pathgeneration unit 210 may calculate a triangular plane using athree-dimensional matrix generating an arc-shaped path in thethree-dimensional space, as shown in FIG. 7, from the position X_(obj)of the target object A, the current position X_(c) of the gripper 131and the target position X_(t) of the gripper 131 using Equation 2 below.n=(x _(c) −x _(obj))/∥x _(c) −x _(obj)∥a=(x _(c) −x _(obj))×(x _(t) −x _(obj))o=a×nR=[noa]  Equation 2

In Equation 2, n is an X axis value of the three-dimensional triangularplane, o is a Y axis value of the three-dimensional triangular plane,and a is a z axis value of the three-dimensional triangular plane.

The path in three-dimensional space along which the gripper 131 needs tomove may be generated by multiplying the three-dimensional matrix Rcalculated by Equation 2 by the x and y coordinates in thetwo-dimensional plane calculated by Equation 1, as stated in Equation 3below.

$\begin{matrix}{\begin{bmatrix}x^{\prime} \\y^{\prime} \\z^{\prime}\end{bmatrix} = {{R\begin{bmatrix}x \\y \\0\end{bmatrix}} + \begin{bmatrix}x_{obj} \\y_{obj} \\z_{obj}\end{bmatrix}}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

In Equation 3, R is a matrix of the three-dimensional triangular plane,

$\begin{bmatrix}x \\y \\0\end{bmatrix}\quad$represents the x and y coordinates in the two-dimensional plane,

$\begin{bmatrix}x_{obj} \\y_{obj} \\z_{obj}\end{bmatrix}\quad$represents the position X_(obj) of the target object A, and

$\begin{bmatrix}x^{\prime} \\y^{\prime} \\z^{\prime}\end{bmatrix}\quad$represents a path X_(t)′ in the three-dimensional space along which thegripper 131 needs to move.

FIG. 8 is a view illustrating an actual path along which the gripper inaccordance with one embodiment moves to grip an object.

In FIG. 8, the gripper 131 may actually move along a path shown in analternating long and short dash line from the current position X_(c) ofthe gripper 131 before the gripper 131 grips the target object A and thetarget position X_(t) of the gripper 131 when the gripper 131 grips thetarget object A.

FIG. 9 is a flow chart illustrating a movement path generation method ofthe gripper of the manipulator of the robot in accordance with oneembodiment.

In FIG. 9, in order to enable the gripper 131 provided at themanipulator 130 to execute an operation to grip the target object A, therecognition unit 220 may recognize the position X_(obj) of the targetobject A, the current position X, of the gripper 131 and the targetposition X_(t) of the gripper 131, and may transmit these positions tothe path generation unit 210 (Operation 300).

Then, the two-dimensional path calculation unit 211 of the pathgeneration unit 210 may calculate an included angle of a triangle formedby connecting the position X_(obj) of the target object A, the currentposition X_(c) of the gripper 131 and the target position X_(t) of thegripper 131 transmitted from the recognition unit 220, i.e., a rotaryangle Ø in a plane, as shown in FIG. 5 (Operation 302).

Thereafter, the two-dimensional path calculation unit 211 of the pathgeneration unit 210 may calculate an arc-shaped path in atwo-dimensional plane along which the gripper 131 needs to move usingthe calculated rotary angle Ø in the plane, as shown in FIG. 6(Operation 304).

The three-dimensional path transform unit 212 of the path generationunit 210 may transform a triangular plane generating an arc-shaped pathin the three-dimensional space, as shown in FIG. 7, from the positionX_(obj) of the target object A, the current position X_(c) of thegripper 131 and the target position X_(t) of the gripper 131 transmittedfrom the recognition unit 220, into a three-dimensional matrix R(Operation 306).

Thereafter, the three-dimensional path transform unit 212 of the pathgeneration unit 210 may generate an actual path in the three-dimensionalspace along which the gripper 131 needs to move, as shown in FIG. 8, bymultiplying the three-dimensional matrix R by the x and y coordinates inthe two-dimensional plane calculated by the two-dimensional pathcalculation unit 211.

As is apparent from the above description, in a manipulator and a pathgeneration method thereof in accordance with one embodiment, a targetobject and a gripper may be modeled into a spherical shape, a currentposition of the gripper, a position of the target object and a targetposition of the gripper may be measured, an arc-shaped path in atwo-dimensional plane along which the gripper needs to move may becalculated by calculating an included angle of a triangle consisting ofthe current position of the gripper, the position of the object and thetarget position of the gripper, the arc-shaped path in thetwo-dimensional plane may be transformed into an arc-shaped path in athree-dimensional space using a transform matrix consisting of thecurrent position of the gripper, the position of the object and thetarget position of the gripper, thereby possibly automaticallygenerating the shortest path of the manipulator to grip the objectwithout collision with the object. Thus, a safe operation path may beachieved and an operation time may be reduced.

The methods according to the above-described example embodiments may berecorded in non-transitory computer-readable media including programinstructions to implement various operations embodied by a computer. Themedia may also include, alone or in combination with the programinstructions, data files, data structures, and the like. The programinstructions recorded on the media may be those specially designed andconstructed for the purposes of the example embodiments, or they may beof the kind well-known and available to those having skill in thecomputer software arts. Examples of non-transitory computer-readablemedia include magnetic media such as hard disks, floppy disks, andmagnetic tape; optical media such as CD ROM disks and DVDs;magneto-optical media such as optical discs; and hardware devices thatare specially configured to store and perform program instructions, suchas read-only memory (ROM), random access memory (RAM), flash memory, andthe like.

Examples of program instructions include both machine code, such asproduced by a compiler, and files containing higher level code that maybe executed by the computer using an interpreter. The described hardwaredevices may be configured to act as one or more software modules inorder to perform the operations of the above-described exampleembodiments, or vice versa. Any one or more of the software modulesdescribed herein may be executed by a dedicated processor unique to thatunit or by a processor common to one or more of the modules. Thedescribed methods may be executed on a general purpose computer orprocessor or may be executed on a particular machine such as the imageprocessing apparatus described herein.

Although a few embodiments have been shown and described, it would beappreciated by those skilled in the art that changes may be made inthese embodiments without departing from the principles and spirit ofthe invention, the scope of which is defined in the claims and theirequivalents.

What is claimed is:
 1. A movement path generation method of amanipulator to grip an object comprising: recognizing a current positionof a gripper provided at the front end of the manipulator, a position ofthe object and a target position of the gripper; calculating, by aprocessor, a rotary angle on a plane defined by the current position ofthe gripper, the position of the object and the target position of thegripper; calculating an arc-shaped path in a two-dimensional plane alongwhich the gripper needs to move using the calculated rotary angle;calculating a transform matrix consisting of the current position of thegripper, the position of the object and the target position of thegripper; and transforming the arc-shaped path in the two-dimensionalplane into an arc-shaped path in a three-dimensional space using thetransform matrix.
 2. The movement path generation method according toclaim 1, wherein the current position of the gripper is a position of astart point of the gripper prior to executing an operation of grippingthe object.
 3. The movement path generation method according to claim 1,wherein the position of the object is a central position of the objectto be gripped.
 4. The movement path generation method according to claim1, wherein the target position of the gripper is a position of a targetpoint of the gripper to grip the object.
 5. The movement path generationmethod according to claim 1, wherein the calculation of the rotary anglein the plane includes calculating an included angle of a triangle formedby connecting the current position of the gripper, the position of theobject and the target position of the gripper.
 6. The movement pathgeneration method according to claim 5, wherein the calculation of thearc-shaped path in the two-dimensional space includes: calculating thesum of a radius of the object and a radius of the gripper; calculatingan included angle by which the gripper moves for a designated time; andcalculating x and y coordinates in the two-dimensional plane to generatean arc-shaped trajectory by multiplying the sum of the radius of theobject and the radius of the gripper by the included angle by which thegripper moves for the designated time.
 7. The movement path generationmethod according to claim 6, wherein the calculation of the transformmatrix includes transforming a triangular plane generating thearc-shaped trajectory from the current position of the gripper, theposition of the object and the target position of the gripper into athree-dimensional matrix.
 8. The movement path generation methodaccording to claim 7, wherein the transformation of the arc-shaped pathin the two-dimensional plane into the arc-shaped path in thethree-dimensional space includes generating the arc-shaped path in thethree-dimensional space along which the gripper needs to move bymultiplying the three-dimensional matrix by the x and y coordinates inthe two-dimensional plane.
 9. A manipulator comprising: a gripper togrip an object; a plurality of links to move the gripper to a targetposition to grip the object; a recognition unit to recognize a currentposition of the gripper, a position of the object and a target positionof the gripper; and a path generation unit to calculate a rotary angleon a plane defined by the current position of the gripper, the positionof the object and the target position of the gripper, and to calculatean arc-shaped path in a two-dimensional plane along which the gripperneeds to move using the calculated rotary angle, the current position ofthe gripper, the position of the object and the target position of thegripper, and to generate an arc-shaped path in a three-dimensional spacealong which the gripper needs to move using the calculated arc-shapedpath in the two-dimensional plane.
 10. The manipulator according toclaim 9, wherein the current position of the gripper is a position of astart point of the gripper prior to executing an operation of grippingthe object.
 11. The manipulator according to claim 9, wherein theposition of the object is a central position of the object to begripped.
 12. The manipulator according to claim 9, wherein the targetposition of the gripper is a position of a target point of the gripperto grip the object.
 13. The manipulator according to claim 9, whereinthe path generation unit includes a two-dimensional path calculationunit to calculate the arc-shaped path in the two-dimensional plane usingthe current position of the gripper, the position of the object and thetarget position of the gripper, and a three-dimensional path transformunit to transform the arc-shaped path in the two-dimensional plane intothe arc-shaped path in the three-dimensional space by calculating atransform matrix consisting of the current position of the gripper, theposition of the object and the target position of the gripper.
 14. Themanipulator according to claim 13, wherein the two-dimensional pathcalculation unit calculates the rotary angle, and calculates thearc-shaped path in the two-dimensional plane along which the gripperneeds to move using the calculated rotary angle.
 15. The manipulatoraccording to claim 14, wherein the rotary angle in the plane is anincluded angle of a triangle formed by connecting the current positionof the gripper, the position of the object and the target position ofthe gripper.
 16. The manipulator according to claim 15, wherein thetwo-dimensional path calculation unit calculates the sum of a radius ofthe object and a radius of the gripper, calculates an included angle bywhich the gripper moves for a designated time, and calculates x and ycoordinates in the two-dimensional plane to generate an arc-shapedtrajectory by multiplying the sum of the radius of the object and theradius of the gripper by the included angle by which the gripper movesfor the designated time.
 17. The manipulator according to claim 16,wherein the three-dimensional path transform unit transforms atriangular plane generating the arc-shaped trajectory from the currentposition of the gripper, the position of the object and the targetposition of the gripper into a three-dimensional matrix, and generatesthe arc-shaped path in the three-dimensional space along which thegripper needs to move by multiplying the three-dimensional matrix by thex and y coordinates in the two-dimensional plane.
 18. The manipulatoraccording to claim 9, further comprising joints to drive the pluralityof links to move the gripper along the path generated by the pathgeneration unit.
 19. A movement path generation method of a manipulatorto grip an object comprising: recognizing a position of a start point ofa gripper provided at the front end of the manipulator, a centralposition of the object and a position of a target point of the gripperto grip the object; calculating, by a processor, a rotary angle on aplane defined by the start point of the gripper prior to executing anoperation of gripping the object, the central position of the object andthe target point of the gripper, wherein the calculation of the rotaryangle in the plane includes calculating an included angle of a triangleformed by connecting the start point of the gripper, the centralposition of the object and the target point of the gripper; calculatingan arc-shaped path in a two-dimensional plane along which the gripperneeds to move using the calculated rotary angle; calculating a transformmatrix consisting of the start point of the gripper, the centralposition of the object and the target point of the gripper; andtransforming the arc-shaped path in the two-dimensional plane into anarc-shaped path in a three-dimensional space using the transform matrix.20. The movement path generation method according to claim 5, whereinthe calculation of the arc-shaped path in the two-dimensional spaceincludes: calculating the sum of a radius of the object and a radius ofthe gripper; calculating an included angle by which the gripper movesfor a designated time; and calculating x and y coordinates in thetwo-dimensional plane to generate an arc-shaped trajectory bymultiplying the sum of the radius of the object and the radius of thegripper by the included angle by which the gripper moves for thedesignated time.